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lite.cnn.com - on gopher - inofficial | |
ARTICLE VIEW: | |
• | |
6 min read | |
Astronomers spot an interstellar object zipping through our solar | |
system | |
By Ashley Strickland, CNN | |
Updated: | |
8:26 PM EDT, Thu July 3, 2025 | |
Source: CNN | |
A newly discovered object speeding through our solar system is sparking | |
excitement among astronomers because it’s not from around here. | |
Believed to be a comet, the object is only the third celestial body | |
from beyond our solar system ever to be observed in our corner of the | |
universe. | |
This interstellar visitor, now officially named 3I/ATLAS, became known | |
when the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert | |
System) telescope in Chile reported spotting it on Tuesday. Since then, | |
astronomers reviewing archival observations from multiple telescopes | |
have tracked the object’s movements as far back as June 14 and found | |
that the comet arrived from the direction of the Sagittarius | |
constellation. | |
The comet’s speed and path through the solar system are two strong | |
indicators that it originated beyond our solar system, said Gianluca | |
Masi, astronomer and astrophysicist at the Bellatrix Astronomical | |
Observatory in Italy and founder and scientific director of the Virtual | |
Telescope Project. Masi has been making observations of the comet and | |
will stream a live view of the object on the beginning at 6 p.m. ET | |
Thursday. | |
The comet is moving at nearly 37 miles per second (60 kilometers per | |
second) — or 133,200 miles per hour (about 214,364 kilometers per | |
hour) — too fast to be a “local” object in our solar system, said | |
Teddy Kareta, an assistant professor at Villanova University near | |
Philadelphia. | |
“Objects bound to the sun — denizens of our solar system — take | |
paths around it that return to the same point,” Kareta wrote in an | |
email. “The Earth’s orbit is mostly circular, Pluto’s orbit is a | |
stretched oval, and many comets are very highly ‘eccentric’ — | |
their orbits are very long and narrow ellipses. This object’s path | |
through the solar system is very nearly a straight line.” | |
Tracking the object’s orbit also reveals the path it has taken to | |
reach our solar system, said Dr. Paul Chodas, director of NASA’s | |
Center of Near-Earth Object Studies at NASA’s Jet Propulsion | |
Laboratory in Pasadena, California. | |
“When we extrapolate its motion backwards in time we see that it | |
clearly originated from outside our Solar System,” Chodas wrote in an | |
email. “It must have originated from another Solar System and | |
probably has been travelling through interstellar space for millions of | |
years until it happened to encounter our Solar System.” | |
Since the initial sighting of the comet, located 420 million miles (675 | |
million kilometers) from Earth, astronomers have rushed to observe the | |
object with telescopes around the world. One of those astronomers is | |
Kareta, who observed the comet, using the Lowell Observatory’s Lowell | |
Discovery Telescope in Flagstaff, Arizona, as soon as he heard about it | |
on the night of its discovery. He said he believes it will only be a | |
couple of weeks before just about every large telescope on Earth and in | |
space has made time to spot and track the comet. | |
“People are excited. Almost every planetary astronomer I know | |
immediately ran to a telescope or sent emails requesting telescope | |
(observing) time in the next few days,” said Kareta, formerly a | |
postdoctoral researcher at the Lowell Observatory. “While we might | |
have several months to study this fascinating object, the earlier we | |
can figure out how it works — how it is evolving, what strange or | |
unexpected properties it might have — the quicker we can plan for the | |
rest of its passage through the solar system.” | |
Anatomy of an interstellar object | |
Comet 3I/ATLAS follows two other intriguing interstellar objects, | |
called ISOs, that once passed through our solar system: in 2017 and in | |
2019. Both objects, also thought to be interstellar comets, stirred | |
intense interest. The of cigar-shaped ‘Oumuamua even ignited claims | |
that it could be an alien probe. | |
Little is known so far about comet 3I/ATLAS. Astronomers estimate its | |
diameter to be 12 miles (20 kilometers), with significant uncertainty | |
due to the object’s brightness, Masi said. | |
However, the comet seems to be the brightest and fastest of the three | |
interstellar objects discovered so far, Kareta noted. | |
3I/ATLAS is approaching our solar system from the Milky Way’s | |
galactic center, a different direction than the previous objects, | |
Chodas said. | |
The object has shown signs of cometary activity, including that it | |
appears to be losing mass like a comet. Comets are made of ice, frozen | |
gases and rock, and as they near stars such as the sun, heat causes | |
them to release gas and dust, which creates their signature tails. But | |
it’s not yet clear what kind of material is releasing from 3I/ATLAS | |
or what process is causing it, Kareta said. | |
“Considering the lingering disagreements about what caused the | |
orbital acceleration of the first ISO ‘Oumuamua, I’d be surprised | |
if diagnosing and understanding this wasn’t a priority for most,” | |
Kareta wrote in an email. “We don’t know where (3I/ATLAS) came from | |
yet, but as our understanding of the object’s orbit (increases) we | |
might be able to make some good guesses in a few months.” | |
The comet’s path | |
Astronomers said that the comet poses no threat to Earth and will | |
remain at least 150 million miles (240 million kilometers) from our | |
planet. The comet is currently about 416 million miles (670 million | |
kilometers) away from the sun and will make its closest approach to our | |
star around October 30 at a distance of 130 million miles (210 million | |
kilometers), according to . | |
The comet will also whip by Mars on October 2 at 18 million miles (30 | |
million kilometers) from the red planet. This is a relatively close | |
pass, astronomically speaking. For reference, Earth is about 93 million | |
miles (150 million kilometers) from the sun. | |
The nearest the comet will come to Earth is 167 million miles (270 | |
million kilometers) on December 19, Masi said. | |
Masi said the comet is currently visible in the Sagittarius | |
constellation, which is best viewed from the southern sky in the middle | |
of the night. While the full moon on July 10 will make 3I/ATLAS | |
difficult to observe, observations even with small telescopes should | |
improve in the coming months, he added. | |
Astronomers expect that the comet will remain visible for ground-based | |
telescope observations through September before disappearing from view. | |
It should reappear on the other side of the sun in early December, | |
enabling follow-up observations. It will be observable well into | |
mid-2026, Chodas said. | |
Further study could reveal whether comets look the same in other solar | |
systems, Kareta said. | |
Studying interstellar objects is also crucial to gaining a broader | |
understanding of planets beyond our solar system and how they form, he | |
added, describing these visitors as “some of the most fascinating | |
things we’ve discovered.” | |
“They’re comets and asteroids which formed around other stars — | |
the building blocks of planets around those faraway stars — which got | |
ejected into interstellar space which we later find as they zip through | |
our solar system,” Kareta said. “We want to measure everything we | |
can about these objects to compare them to our own local comets and | |
asteroids. They’re big questions, but the fact that we can make any | |
progress on them by studying these fascinating objects should tell you | |
why planetary astronomers are so excited to learn everything we can | |
about them.” | |
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